Hydrogen atom abstraction by p-chloranil triplet from tetrachlorohydroquinone and the presence of a competitive deactivation process

Kobashi, Harumichi; Nagumo, Takashi; Morita, Tomoaki

doi:10.1016/0009-2614(78)85528-6

Chemical Physics Letters

1978

DOI: 10.1016/0009-2614(78)85528-6

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Hydrogen atom abstraction by p-chloranil triplet from tetrachlorohydroquinone and the presence of a competitive deactivation process

Harumichi Kobashi

Takashi Nagumo

Tomoaki Morita

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Cited by 9 publications

(1 citation statement)

References 23 publications

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“…In order to compare the obtained experimental data with the theoretical curves, we need to fix several values of parameters in (10). First, we replace the vibrational frequencies of chloranil in the LE and CT configurations with those of free Tt chloranil and the anion radical, respectively.…”

mentioning

confidence: 99%

Transient Raman studies on the structure of the chloranil-alkylbenzene triplet charge-transfer complexes

Tahara¹,

Hamaguchi²

1992

J. Phys. Chem.

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Transient resonance Raman spectroscopy has been used to study the structure of chloranilalkylbenzene triplet chargetransfer complexes in solution. Resonance excitation conditions were chosen so that only Raman bands due to chloranil vibrations were selectively enhanced. The Raman spectra of the complexes with weak donors were similar to that of TI chloranil, while those of the complexes with strong donors were similar to that of the chloranil anion radical. The observed vibrational frequencies of chloranil in the triplet complexes were plotted as a function of the ionization potential of donors, and common "S-shape (or inverted S-shape)" dependence was observed for all the vibrations. This S-shape dependence was well-reproduced by a simple theory. It was concluded that the molecular structure of the chloranil moiety in these triplet complexes is intermediate between that of the free TI state and that of the anion radical. The structure changes in accordance with the change in the electron-donating ability of donors, reflecting the change in the magnitude of the charge transfer occurring in the complexes.

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mentioning

confidence: 99%

Transient Raman studies on the structure of the chloranil-alkylbenzene triplet charge-transfer complexes

Tahara¹,

Hamaguchi²

1992

J. Phys. Chem.

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Competitive Decay Pathways of the Radical Ions Formed by Photoinduced Electron Transfer between Quinones and 4,4′-Dimethoxydiphenylmethane in Acetonitrile

Giacco¹,

Baciocchi²,

Lanzalunga³

et al. 2001

Chem. Eur. J.

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The reactivity of the cation radical of (4-MeOC6H4)2CH2 photosensitized by 1,4-benzoquinone (BQ), 2,5-dichloro-1,4-benzoquinone (Cl2BQ), and tetrachloro-1,4-benzoquinone (chloranil, CA) was investigated in acetonitrile. The main photoreaction products obtained by steady-state irradiation were identified to be: (4-MeOC6H4)2-CHOC6H4OH, sensitized by BQ; (4-MeOC6H4)2CHCl, sensitized by Cl2BQ; (4-MeOC6H4)2CHOH, sensitized by CA. The mechanism of their formation was investigated by nanosecond laser flash photolysis that allowed transient species (radical ions, neutral radicals, and ions) to be detected and characterized in terms of absorption spectra, formation quantum yields, and decay rate constants. For all systems, the interaction between the triplet quinone (Q) and (4-MeOC6H4)2CH2 produced the corresponding radical ions (quantum yield phi > or = 0.72) which mainly decay by back electron transfer processes. Less efficient reaction routes for the radical ions Q*- and (4-MeOC6H4)2CH2*+ were also: i) the proton-transfer process with the formation of the radical (4-MeOC6H4)2CH* by use of Cl2BQ; ii) the hydrogen-transfer process with the formation of the cation (4-MeOC6H4)2CH+ in the case of CA. Instead. BQ sensitized a much higher yield of BOH* and (4-MeOC6H4)2CH*, mainly by the direct interaction of triplet BQ with (4-MeOC6H4)2CH2. It was also shown that the presence of salts decreases significantly the rate of the back electron transfer process and enhances the quantum yields of formation of the neutral radicals and ions when Cl2BQ and CA are used, respectively. The behavior of BQ*-, Cl2BQ*-, and CA*- appears to be mainly determined by the Mulliken charges on the oxygen atom obtained from quantum mechanical calculations with the model B3LYP/6-311G(d,p). Spin densities seem to be much less important.

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Intermediates in the reactions of electronically excited chloranil with heterocylic compounds

et al. 1984

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Hydrogen atom abstraction by p-chloranil triplet from tetrachlorohydroquinone and the presence of a competitive deactivation process

Cited by 9 publications

References 23 publications

Transient Raman studies on the structure of the chloranil-alkylbenzene triplet charge-transfer complexes

Transient Raman studies on the structure of the chloranil-alkylbenzene triplet charge-transfer complexes

Competitive Decay Pathways of the Radical Ions Formed by Photoinduced Electron Transfer between Quinones and 4,4′-Dimethoxydiphenylmethane in Acetonitrile

Intermediates in the reactions of electronically excited chloranil with heterocylic compounds

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